The purpose of the research outlined in this proposal is to discover multiple predictors of the ability to tolerate pain. These predictors will bw sought in the response systems which are regarded as components of the human experience of pain. The theoretical construct which will integrate the search through these response systems is the notion of level of arousal both in the CNS as a valance between cortical excitation and inhibition, and in the various subsystems of the ANS. Intense stimulation is generally regarded as one of the essential components of a painful experience. Different individual levels of initial arousal and abilities of modulate stimulation should then play a role in mediating the esperience of pain. The different response systems which will be trapped in order to probe the relationship between pain and level of arousal are: the cognitive awareness of the subject through self report, the subsystems of the ANS under resting conditions, immediately prior to a signalled stress and during stress, and the CNS insofar as it manifests the tendency to modulate or augment/reduce incoming stimulation. Several different methods will be used to investigate these systems. Psychometric instruments will be employed to measure subjective cognitive awareness of arousal. These will include the Eysenck Personality Inventory, the Sensation Seeking Scale and the Autonomic Perception Questionnaire. Also the Kinesthetic After Effects Test and the Reducer-Augmenter Test will be examined as psychometric measures of the tendency to modulate sensory input. Physiological measures of various ANS subsystems will be obtained in the resting, signalled prestress and stressed states. Evoked potentials will be used to measure the tendency of the CNS to augment or reduce incoming stimulation.